I don't know where the idea that we can only digest so much protein at a time came from, though I suspect it was in part from the people who sell protein supplements.

What happens to the protein we are unable to digest? It's not water. It's food. Why would our bodies dispose of food? It just doesn't work that way.

From my own experience and from a logic point of view any excess protein, ie calories, that I don't use will just add to my bodyfat. Why wouldn't it? It's just excess calories, the same as excess carbs would.

Obviously, if you are a musclebound monster then your need for calories, whether they are from protein, carbs or fat may well include 2g per lb of bodyweight of protein. Might even be more. But I doubt that's the norm.

I agree with Eazy that it's a myth that we need to eat protein every three hours or so. That just doesn't make sense either. If you eat the same amount during the course of twenty four hours, whether you eat it every three hours or every six, it will amount to exactly the same intake of amino acids/calories etc etc.

The only possible time I can see when we might need to add extra (faster digesting) protein is post workout, when we need to start the process of rebuilding torn muscle tissue. And that is only so we can start the process a bit quicker than waiting for the next meal in four or five hours.

If we've just eaten a load a protein before working out (not me, I can't work out with a belly full of tuna or beef) then adding extra would probably not make a lot of difference.

I expect there will be plenty who disagree, but that's my understanding.